Thermally assisted microbot transport through high-viscosity media

Many potential in vivo microbot (µbot) applications require transport through high-viscosity environments. We have previously demonstrated that rotating magnetic fields can be used to reversibly assemble and drive µbots composed of paramagnetic microparticles. In this, particle surface chemistry can be readily manipulated and the combination of chemical degradation and mechanical action used to enhance penetration of µbot swarms into gelled networks. Here we show that a thermal approach, created through a hyperthermia-induced heating of microparticles with complementary alternating magnetic fields, can also be used to enhance mechanical action by lowering local viscosity. In addition, we observe that a rapid µbot back and forth sweeping motion induced by the applied field significantly improves penetration rates by reducing both µbot size and viscous resistance.